NOD1 and infection: The two major pathways are the nucleotide-binding oligomerization domain-containing protein 1 (NOD1)-dependent activation of p38-MAPK pathway promoted by the H. pylori type 4 secretion system (T4SS) components including the effector protein CagA and peptidoglycan fragments,403 and the CagA-dependent activation of sonic hedgehog signaling pathway.404 Infection by H. pylori also negatively affects the expression of PD-L1 suppressor miRNAs, such asmiR-132 and miR-200b, which partially contribute to the elevated PD-L1 expression in H. pylori-positive GC405 (Fig. 3b).